Global Routing Operations D. Plonka
Network Working Group University of Wisconsin
Request for Comments: 4085 June 2005
BCP: 105
Category: Best Current Practice
Embedding Globally-Routable Internet Addresses Considered Harmful
Status of This Memo
This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document discourages the practice of embedding references to
unique, globally-routable IP addresses in Internet hosts, describes
some of the resulting problems, and considers selected alternatives.
This document is intended to clarify best current practices in this
regard.
Table of Contents
1. Introduction ....................................................2
2. Problems ........................................................2
3. Recommendations .................................................4
3.1. Disable Unused Features ....................................4
3.2. Provide User Interface for IP Features .....................4
3.3. Use Domain Names as Service Identifiers ....................4
3.4. Use Special-Purpose, Reserved IP Addresses When Available ..5
3.5. Discover and Utilize Local Services ........................6
3.6. Avoid Mentioning the IP Addresses of Services ..............6
4. Security Considerations .........................................6
5. Conclusion ......................................................7
6. Acknowledgements ................................................7
7. References ......................................................7
Appendix A. Background ............................................9
Plonka Best Current Practice [Page 1]RFC 4085 Embedding IP Addresses Considered Harmful June 20051. Introduction
Some vendors of consumer electronics and network gear have
unfortunately chosen to embed, or "hard-code", globally-routable
Internet Protocol addresses within their products' firmware. These
embedded IP addresses are typically individual server IP addresses or
IP subnet prefixes. Thus, they are sometimes used as service
identifiers, to which unsolicted requests are directed, or as subnet
identifiers, specifying sets of Internet addresses that the given
product somehow treats specially.
One recent example was the embedding of the globally-routable IP
address of a Network Time Protocol server in the firmware of hundreds
of thousands of Internet hosts that are now in operation worldwide.
The hosts are primarily, but are not necessarily, limited to low-cost
routers and middleboxes for personal or residential use. In another
case, IP address prefixes that had once been reserved by the Internet
Assigned Numbers Authority (IANA) were embedded in a router product
so that it can automatically discard packets that appear to have
invalid source IP addresses.
Such "hard-coding" of globally-routable IP addresses as identifiers
within the host's firmware presents significant problems to the
operation of the Internet and to the management of its address space.
Ostensibly, this practice arose as an attempt to simplify IP host
configuration by pre-loading hosts with IP addresses. Products that
rely on such embedded IP addresses initially may appear to be
convenient to the product's designer and to its operator or user, but
this dubious benefit comes at the expense of others in the Internet
community.
This document denounces the practice of embedding references to
unique, globally-routable IP addresses in Internet hosts, describes
some of the resulting problems, and considers selected alternatives.
It also reminds the Internet community of the ephemeral nature of
unique, globally-routable IP addresses; the assignment and use of IP
addresses as identifiers is temporary and therefore should not be
used in fixed configurations.
2. Problems
The embedding of IP addresses in products has caused an increasing
number of Internet hosts to rely on a single central Internet
service. This can result in a service outage when the aggregate
workload overwhelms that service. When fixed addresses are embedded
Plonka Best Current Practice [Page 2]RFC 4085 Embedding IP Addresses Considered Harmful June 2005